Conventional drill bits have been used in the past to bore holes into a workpiece. Typically, such bits position a cutting surface around an axis of the bit, and the bit is rotated at high speed around the axis using a rotary power tool such as a hand drill or a drill press. The rotating cutting edge of the bit bores a circular opening as the bit is advanced into the workpiece.
Standard drill bits may be configured to be of a generally uniform radial size so that a single bit is adapted to produce a hole of a single radius. To promote space savings and to reduce the need to own a large number of standard drill bits, stepped drill configurations have been developed wherein a generally conically shaped bit includes a plurality of graduated, stepped shoulders. The shoulders are of progressively smaller diameters as they are arranged concentrically on the bit axis toward the tip of the bit. The shoulders typically include one or more cutting edges which are defined by a longitudinally extending slot in the side of the bit. The stepped drill bit conveniently may be used to bore openings of varying sizes without the need to change the bit in the power tool.
In the past, these stepped drill bits had shortcomings in their durability and stability. For example, in order to increase the number of cutting edges on each shoulder, one or more additional slots were formed in the side of the bit. The additional slot or slots may decrease the structural integrity of the bit, however, since the amount of material stabilizing the bit structure is decreased. Furthermore, because multiple slots cause the walls of each shoulder to be of decreased arc length, there is less surface to guide each shoulder as it bores its respective hole in the workpiece. This leads to instability and vibration of the bit during its rotation and may compromise the uniformity of the openings that are formed in the workpiece.